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Thread: The relation between "checkpoint_timeout" and "checkpoint_warning" is missing

The relation between "checkpoint_timeout" and "checkpoint_warning" is missing

From
Tianyin Xu
Date:
Hi, PG,

In "18.5.2. Checkpoints" (http://www.postgresql.org/docs/9.2/static/runtime-config-wal.html#RUNTIME-CONFIG-WAL-CHECKPOINTS), the relation between "checkpoint_timeout" and "checkpoint_warning" is missing. 

According to the code, "checkpoint_timeout" should be set larger than "checkpoint_warning", otherwise the warnings will not be generated. The comments in function: CheckpointerMain() also tell such behavior, which is in line#473 in "src/backend/postmaster/checkpointer.c":

/*
 * We will warn if (a) too soon since last checkpoint (whatever
 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
 * since the last checkpoint start.  Note in particular that this
 * implementation will not generate warnings caused by
 * CheckPointTimeout < CheckPointWarning.
 */

I think this's should definitely specified in the documentation.

Best,
Tianyin 

Re: The relation between "checkpoint_timeout" and "checkpoint_warning" is missing

From
Peter Eisentraut
Date:
On Fri, 2013-02-08 at 01:38 -0800, Tianyin Xu wrote:
> In "18.5.2. Checkpoints" (
> http://www.postgresql.org/docs/9.2/static/runtime-config-wal.html#RUNTIME-CONFIG-WAL-CHECKPOINTS),
> the relation between "checkpoint_timeout" and "checkpoint_warning" is
> missing.

Fixed.  Thanks for the suggestion.